Sunday, December 9, 2007

Thoughts on elevation

Friday's snow bike ride with JayP was part training, part exploration, and part experiment. In addition to checking out part of the Togowotee Winter Classic 100-mile course, I wanted to capture some ride data and compare the results using the tools that I have. The main number I was interested in was elevation gain.

On the handlebars I had my trusty Polar 720i HR monitor as well as my Garmin eTrex Vista HCX to capture a track log. Both will capture elevation gain.

Step #1 - download file from Polar 720i into the Polar Performance Software. Elevation gain = 2,119'

Polar Performance Software Graph

Step #2 - Upload the file from the Polar into Training Peaks. Elevation Gain = 2,700'

Training Peaks Graph from Polar 720i file

Step #3 - Download file from Garmin eTrex HCX to National Geographic TOPO!. Choose "build profile" option from Route. Elevation Gain = 1,474'

National Geographic TOPO! Map & Profile

Step #4 - Download the same track file directly from the Garmin into Garmin's MapSource Software. Track is created but no elevation gain number is created.

Step #5 - Using MapSource, take .GDB file that was created when I downloaded the track, then save the track file as a .GPX file and upload to MotionBased. File can be viewed here. Elevation gain = 2,866'.

I used two tools to capture the data and four tools to look at the data. This resulted in four different elevation gain numbers. Arghh!

7 comments:

Rick L. said...

Extreme: Kudos on the effort to capture those elusive elevation numbers. If you can't nail it down, I don't know who can. I do know there's lots 'o hills around Togwotee. Perhaps some kind of moose-mounted, positive-ion-inducing, beer-activated...nah. Let's just ride.

JenyJo said...

well, how much elevation gain did it FEEL like?

glad to hear you'll be playing in the susitna!!! good luck to you both!!!

hope you guys are doing well!

jj

Cellarrat said...

Gotta love measurements that rely on barometric pressure!

Dave Harris said...

Here's another batch of numbers for ya generated from TopoFusion. Digital Elevation data was used which replaces your unit's elevation data...

TopoFusion: 2989 ft
Straight GPS: 2991 ft
Straight DEM: 2991 ft
Maptech: 1773 ft
TopoUSA: 3067 ft
Custom Algorithm: 2989 ft

Who is right? Scott Morris could tell ya more than you want to know.

Dave Byers said...

DH - it is interesting that Motion Based and TopoFusion were so close. When you use TopoFusion, are you downloading directly from the GPS into the software or using the Garmin software to save it as a .GPX file?

Dave Harris said...

Dave - direct downloads to/from TopFusion. You can upload tracks to the active log or stored tracks, or as a route.

fizgig said...

I've run into this same issue, anywhere between 900' and 2400' for a single GPX file